1. Field Of The Invention
The invention relates to surface-modified magnesium hydroxide or aluminum hydroxide particles, to the use thereof in thermoplastic polyolefins, and to flame-retardant thermoplastic polyolefins containing the magnesium hydroxide or aluminum hydroxide which has been surface-modified according to the invention.
2. Background Art
On incorporation of magnesium hydroxide or aluminum hydroxide into plastics, problems occur on the one hand with the incorporation of the magnesium hydroxide or aluminum hydroxide into the plastic and compatibility thereof with the plastic, and on the other hand the plastic treated with magnesium hydroxide or aluminum hydroxide must satisfy the required properties, in particular with respect to fire behavior. There has, therefore, been no lack of effort to modify flame-inhibiting fillers in such a manner that they can be incorporated without difficulties into the plastics without adversely affecting the property profile of the plastic, particularly with respect to the fire behavior.
Thus, for example, German Patent No. 2,659,933 discloses coating magnesium hydroxide with anionic, surface-active substances, such as, with alkali metal salts of higher fatty acids. As made clear by our comparative experiments below, magnesium hydroxides modified in this way cannot meet the demands placed on them.
European Published Application No. 292,233 furthermore discloses coating fillers, such as, magnesium hydroxide or aluminum hydroxide, with a polymer containing unsaturated acid groups and incorporating the product into an olefin/acrylate polymer. For example, magnesium hydroxide or aluminum hydroxide is coated in a matrix polymer with a maleinate polybutadiene. However, the polybutadiene coatings, also known as liquid-elastomeric coatings, have the great disadvantage, due to the numerous double bonds, of being very susceptible to the effects of UV and ozone, i.e., the property profile of the correspondingly treated filler or of the filler-containing compound worsens under such effects. In addition, the choice of compounding unit when compounding a filler modified in this way into a plastic is limited by the low temperature tolerance of the coating.